HIV/AIDS continues to affect the Latino community disproportionately, with more than 200,000 cases in the US attributed to this population. Puerto Ricans living on the Caribbean island have among the highest prevalence rates of HIV among Latinos, a pattern that is closely connected to the large and growing injecting drug epidemic in Puerto Rico. While intravenous drug injection practices have been studied in Puerto Rico, certain vulnerable populations and injection practices have been largely neglected. This proposal focuses on male-to-female transgendered persons (MTF-TG), who are generally absent from the scientific literature generated in Puerto Rico, and are at high risk of HIV infection. In addition to the fact that MTF-TG are embedded in an HIV epidemic that is mostly driven by injecting drug use, our preliminary studies show that they engage in body modification practices involving the use of illegal market hormone and silicone injections. Our community partners, who are conducting the only HIV prevention intervention with MTF-TG, indicate that members of this population often engage in self-injection practices during pumping parties for the purpose of body modification, as well as during drug use. These practices have not been scientifically studied, nor are there focused descriptive studies of the social context, meanings, and practices of injection in this population. Therefore, our study aims to: (1) identify the meanings and practices of drug and hormone injection in the transgendered community in Puerto Rico; (2) describe and map the social contexts of drug and hormone injection in this population; and (3) document the relationship between drug, hormone, and silicone injection practices and risk for HIV in Puerto Rico. We will conduct qualitative interviews with 32 theoretically sampled MTF-TG; ethnographic mapping of the social contexts of drug, silicone, and hormone injection among MTF- TG; and surveys with 96 MTF-TG recruited through respondent-driven sampling (RDS). Led by a team of NIH- funded HIV/AIDS researchers with experience with transgendered persons and vulnerable populations in this cultural region, the study will yield important information on risk practices that have been overlooked in this community and will provide detailed descriptions of the social contexts in which they occur. This will help guide future pilot interventions aimed at reducing HIV infection and high-risk drug use and injection practices in this vulnerable group.